Alpiq in action: Nant de Drance, 1700 tonnes of concrete immersed in Lac d'Emosson

The intake/discharge structure was therefore built on a platform on the south-western shore of the reservoir, following which the construction was filled with air and dragged around 930 meters over Lac d'Emosson by means of an enormous pontoon. From there the gigantic component was lowered centimetre by centimetre until, around 24 hours later, it reached its destination 120 meters below the surface of the lake. This technical feat is based on the principle of the diving bell, and is a first in Switzerland. The procedure has never before been used to install such a construction under water.